1. Field of the Invention
The present invention relates to a method for fabricating ribs of a plasma display panel (PDP). More particularly, the present invention provides a simplified process for fabricating the ribs of a PDP.
2. Description of the Prior Art
Plasma display panels (PDP) are flat panel displays that use a discharge gas to create glowing images on a screen. The PDP has many beneficial characteristics, such as thin, lightweight design, large display sizes and a wide viewing angle.
The PDP has ribs that serve to isolate individual discharge cells from each other, both electrically and optically. The ribs also provide support between the front and rear plates of the PDP. Currently, the fabrication of the ribs of a PDP is the most difficult part of the PDP fabrication process. Hence, improving the rib fabrication process is an important issue in the PDP industry.
Please refer to FIG. 1 to FIG. 4. FIG. 1 to FIG. 4 are cross sectional diagrams of a prior process for fabricating ribs 12 using a sandblasting method. The prior art PDP (not shown) comprises a transparent plate (not shown) and a glass substrate 10 that is positioned behind the transparent plate. In the sandblasting method shown in FIG. 1, solid print of a glass paste is used two or three times to form a glass paste layer 14 onto the glass substrate 10. Next, a dry film photoresist 16 is layered onto the glass paste layer 14.
An exposure process is performed to define the pattern of the ribs 12. The exposure process uses ultraviolet (UV) radiation 20 and a photo-mask 18 to selectively irradiate portions of the photoresist 16. The irradiated. portions of the dry film photoresist 16 are hardened and thus transmit the pattern of the photo-mask 18 onto the dry film photoresist 16. As. shown in FIG. 2, a development process is carried out to remove the dry film photoresist 16 that hasn""t been exposed to the UV radiation 20. The exposed dry film photoresist 16 remains on the glass paste layer 14 and defines the pattern of the ribs 12.
As shown in FIG. 3, after the development process, a sandblasting process is performed. The exposed dry film photoresist 16 protects the glass paste layer 14 below it. A portion of the glass paste layer 14 not covered by the dry film photoresist 16 is removed by the sandblasting process. Then, as shown in FIG. 4, a stripping process removes the remaining dry film photoresist 16, and a firing process is then performed. The glass substrate 10 is heated to 550xc2x0 C., which fuses the remaining glass paste layer 14, for forming the ribs 12.
The sandblasting method according to the prior art manufactures ribs 12 with narrow width and even height, but some constraints are imposed by using the dry film photoresist 16. In the sandblasting process, sand is sent at high speed towards the glass substrate 10, the dry film photoresist 16 must adhere tightly to the glass paste layer 14. However, the dry film photoresist 16 may peel from the top of the glass paste layer 14 under the friction of the sand blasting process when the adhesion of the dry film photoresist 16 is poor. Moreover, the dry film photoresist 16 needs to be removed completely by a suitable machine after the sandblasting step. Therefore, the dry film photoresist 16 should be stripped from the glass paste layer 14 easily. Hence, adhesion characteristics of the dry film photoresist 16 to the glass paste layer 14 should be considered carefully. In summary, characteristics of the dry film photoresist includes strong adhesion to the glass paste, high resistance against sand blasting, and easy removal after the sandblasting process. However, this complicates the manufacturing process, giving rise to higher costs.
Please refer to FIG. 5 and FIG. 6. FIG. 5 and FIG. 6 are schematic diagrams of a prior process for fabricating the ribs 12 of a PDP using a screen printing method. As shown in FIG. 5, the screen printing method uses a scraper 22 to print a glass paste 13 through a screen 24 onto a predetermined area of the glass substrate 10.
As shown in FIG. 6, the screen printing steps are repeated six to twelve times to form the glass paste 13 over the glass substrate 10. The glass paste 13 is stacked until the thickness reaches a predetermined thickness, such as 150 xcexcm to 200 xcexcm. Finally, a firing process is employed to heat the glass substrate 10 until the temperature rises to between 50xc2x0 C. and 600xc2x0 C. Under such high temperatures, the stacked glass paste 13 fuses to form the ribs 12.
In the screen printing method, a dry film photoresist is not used and less glass paste is consumed. However, the screen printing method has poor precision control, and this is a disadvantage in the fabrication of high-resolution PDPs. It is very difficult to control with precision a multi-layer printing process, and so the screen printing method is unable to form ribs with a narrow width. The resolution of the PDP cannot, therefore, be further enhanced. Moreover, the complexity of the manufacturing process is proportional to the number of times that the printing process is performed. The multi-layer printing process increases manufacturing time, and also forms ribs 12 with a non-uniform thickness.
Therefore, a primary objective of the present invention is to provide a method for fabricating ribs of a plasma display panel to solve the above mentioned problems which use the sandblasting method or the screen printing method.
According to the present invention, a method for fabricating ribs of a plasma display panel (PDP) is provided. The PDP comprises a glass substrate. In the method, a solid printing process is first performed to form a first paste layer on the glass substrate. Next, a screen printing process prints a second paste layer onto a first predetermined area of the first paste layer. The second paste layer includes the same rib materials as the first paste layer and a photo-active hardener, such as polyvinyl cinnamate. An exposure process is then employed to activate the photo-active hardener, and causing the second paste layer to be harden. Then, a sandblasting process removes those portions of the first paste layer that are not covered by the second paste layer, the hardened second paste layer acting as a hard mask. Finally, a heating process removes the hardener from the second paste layer and fuses the first paste layer to the second paste layer to form a plurality of ribs.
There is no dry film photoresist used in the aforementioned process, and the printing process is performed only a few times. Thus, the present method simplifies a more complicated process and reduces production time and costs.
These. and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.